Fish stocks off the U.S. coasts, restored to health over the past four decades by cooperation among competing interests and careful management, are threatened anew by warming and increasingly acidic waters, according to a new report and experts who are gathering in Washington this week for a conference on the future of fisheries.

The report, released Saturday by the Pew Charitable Trusts and the Ocean Conservancy, hails the 1976 Magnuson-Stevens Fishery Conservation and Management Act and subsequent amendments for bringing commercial and recreational fishermen, marine scientists and legislators together to ensure that fish populations would be sustained.

As Congress approaches another reauthorization of the law, the report says that salmon, scallop and other sea life populations have been brought back from the brink of collapse to a healthy and sustainable state, largely through enforced catch limits.

The “domestic harvest, export, distribution, and retailing of seafood in America .?.?. generates more than $116 billion in sales and employs more than 1 million people, according to the report. “Recreational fishing adds nearly $50 billion and more than 327,000 jobs to that total.

Connie Barclay, spokeswoman for NOAA Fisheries, said that acting administrator Sam Rauch had not yet read the report but “we welcome stakeholders’ input as we move toward reauthorization of the Magnuson-Stevens Act. The National Oceanic and Atmospheric Administration is hosting this week’s conference.

More complex problems loom, ones that cannot be solved area by area, experts say. “What we need to pay greater attention to is a changing world and a changing climate and what repercussions that will have, Chris Dorsett, director of the Ocean Conservancy’s fish conservation and gulf restoration program, said in an interview.

Chief among those issues is the increasing temperature of the oceans, said Lee Crockett, head of Pew’s U.S. fisheries campaign. North Atlantic waters last summer were the warmest in 159 years of record-keeping, he said.

Off the coast of Maine, lobsters are molting six weeks to two months earlier than normal, and blue crabs, a Mid-Atlantic shellfish, have been found in New England waters as they and other sea life move toward Earth’s poles to escape warmer seas, Crockett said.

The sea today is 30 percent more acidic than it was during pre-industrial times. Increasing amounts of carbon in the water lowers the water’s pH and causes it to eat away at protective shells and the bony structures of coral, Dorsett said.

Conservationists say that fisheries managers must begin to adapt to such changes, primarily by managing whole ecosystems, according to the report.

Instead of the “fish first, ask questions later, approach of the past, Crockett said, “let’s find out what’s appropriate and not appropriate before the fishing starts.

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